This invention relates to an apparatus provided with a floating tool for drilling boring, flaring and other machining work, by using jigs where the working depth is to be precisely set.
In particular, this invention concerns an apparatus to be applied to NC automatic machines, with 5 or more degrees of freedom, for drilling flaring and the like, such machining requiring, particularly in the aeronautics industry, the use of an apparatus suitable for both adjusting possible inaccuracies when positioning the tool with respect to the jig hole axis, and for checking the machining depth in a very limited range of tolerance.
The apparatus is expected to be applied to the machines already known, e.g., from U.S. Pat. No. 5,014,542 and consisting of a movable support along three cartesian axes where a movable tool-holder head is installed and which rotates around two orthogonal axes. Generally, the apparatus may translate along its axis for carrying out the machining required.
The invention relates in particular to, but is not limited to, the field of aeronautic construction and aims at the automation of several machining steps through a numerical control computerization thus replacing the previous manual work, but at the same time keeping their general features. The invention as claimed is intended to provide an apparatus suitable for turning some of the manual machining operations into automatic operations while preventing possible inaccuracies in the tool positioning. As noted above, aeronautical construction is one of the main fields where the apparatus can be applied in accordance with the invention, where parts assembling requires for drilling several holes with flaring is within a limited range of tolerance that is often not over a few 100ths of a mm. The parts to be machined are often curved, which complicates things in a manner so that up to now most holes have been drilled manually with the help of special tools and jigs.
Such known systems were based on the use of a jig provided with bushes and to be applied to the workpiece, then the operator is to carry out the different machining steps manually. Obviously, in spite of the accuracy and care taken, a system like that ensures neither a perfect repeatability of the results nor the observance of the working time set depending on the operator's capability and conditions. Moreover, the working time is quite long.
On the other hand, the complete automation of such machining steps is not possible, in particular for parts which were previously jig-machined, since programming for such a machine arrangement would be remarkable expensive and the different parts would be certified again with a great waste of time and money.
For these reasons, there is a need for apparatuses enabling automation while continuing to use the jigs.
The practical difficulties found are several and related to the need for both centering the tool on the hole to be drilled and checking accurately the tool stroke with respect to the surface to be machined since its position is not previously known even with respect to the jig.